[doc] Clean up setup instruction pages.

Rename "Getting started" to "setup" so users are less tempted to start
with these pages (which assume you've already installed dependencies and
built software). And just in case, also link back to the main "Getting
Started" page from each one.

Signed-off-by: Jade Philipoom <jadep@google.com>

clean up build sw

doc/ug/hw_design.md

diff --git a/doc/ug/hw_design.md b/doc/ug/hw_design.md
index 46783f9..ea21437 100644
--- a/doc/ug/hw_design.md
+++ b/doc/ug/hw_design.md
@@ -1,5 +1,5 @@
 ---
-title: "Getting Started Designing Hardware"
+title: "Designing Hardware"
 ---
 
 This document aims to clarify how to get started with a hardware design within the OpenTitan project.